As smart terminals are developing rapidly, and there are constantly growing demands of subscribers for a transmission rates and a capacity of data services, traditional networks with a single layer of coverage by a macro eNB have failed to satisfy the demands of their subscribers for the data services; and at present, the network scenarios where layered networks are deployed have been introduced by the 3rd Generation Partnership Project (3GPP) to address this problem, and also the bearer splitting technologies and architecture have been introduced so that terminals can access cell resources of multiple eNBs concurrently to thereby enhance mobility management on the terminals, and improve a peak rate for the transmission rate of the data services of the terminals.
At present, a data packet for a split bearer is typically processed in such a way that a data packet discard timer is started for a Packet Data Convergence Protocol (PDCP) Service Data Unit (SDU), and the PDCP SDU data packet for the split bearer is discarded according to the discard timer, that is, the PDCP entity starts a discard timer for a PDCP SDU for each split bearer upon reception of the PDCP SDU, and if the discard timer exceeds a preset length of time, then the PDCP SDU data packet for the split bearer corresponding to the discard timer is discarded; and a preset length of time of a discard timer preset for a PDCP SDU for a different split bearer (the PDCP SDU is allocated for transmission on a Master base station (MeNB) or a Secondary base station (SeNB)) is different due to a delay via an X2 interface between aggregated base stations.
With the network scenario of layered network deployment, and the bearer splitting technologies and architecture, the same split bearer of a User Equipment (UE) is mapped onto logical channels of multiple aggregated base stations for transmission, where the aggregated base stations include a master base station and secondary base stations; and the split bearer is transmitted by the multiple aggregated base stations sharing a PDCP entity located in the master base station, and UE RLC entities for the different aggregated base stations need to be configured separately. While the split bearer is being transmitted, the aggregated base stations notify the UE of PDCP Protocol Data Units (PDUs) of the split bearer, and in the meantime, the PDCP entity located in the master base station stores the PDCP PDUs or the PDCP SDUs notified to the secondary base stations. If there is a change in the secondary base stations serving the same split bearer, where the change in the secondary base stations includes an increase or decrease in the number of secondary base stations, a change of secondary base station, and reconfiguration of some secondary base station, but there is no change in the master base station of the split bearer, then there will be a change in the transmission architectures of the bearer at the UE and network sides, but the behaviors at the UE and network sides in the existing procedure of changing a cell in carrier aggregation have failed to address processing of a PDCP SDU data packet for a split bearer in the scenario of bearer splitting, particularly reporting of a transmission state of the PDCP SDU data packet for the split bearer, processing of the PDCP SDU data packet, transmission of an end indication, etc.
In summary, in the network scenario of layered network deployment, and the hearer splitting technologies and architecture in the prior art, there has been absent so far a corresponding solution to processing of a PDCP SDU data packet for a split bearer if there is a change in the secondary base stations serving the same split bearer.